Telautograph control system



G. R. CLARK TELAUTOGRAPH CONTROL. SYSTEM Feb. 28, 1950 Filed Jan. 24, 1946 INVENTOR. 6715597 A. CIA/PA A TTOiP/VEY Patented Feb. 28, 1950 UNITED STATES =PATENT OFFICE.

- 2,498,649 g f i v i TELAUTO'GRAPH oofirnoL SYSTEM GilbertR. Clark, Nutley, N. J., assignor to Federal Telephone and Radio Corporation, New York, N. Y., a corporation of Delaware 3 Application January 24, 1946, Serial N o 643,10

' 10 Claims. ((1178-48) vide an improved cathode-ray tubetelautograph 5 system.

Another object is to provide a telautograph system employing a cathode-ray tube oscilloscope reproducer, in conjunction with means for reducing the effects of interference on the teleautocathode-ray tube oscilloscope type, by subjecting the received telautograph coordinate signals to the action of'a harmonic filter before applying the said signals to the deflecting elements of the cathode-ray tube.

A feature of the invention relates to a cathodeceiving alternately transmitted coordinate voltages such as may be produced by a telautograph transmitter, and the filtering of these voltages by a pair of harmonic filters eachof which is connected through suitable switching arrangem'ents effective alternately in storing the received coordinate voltages and releasing of the stored -X and Y voltages simultaneously to the beam-deflecting elements of the cathode-ray tube oscilloscope. 1

Another feature relates to a cathode-ray tube oscilloscope which is controlled by coordinate voltages such as those produced'bya telautograph transmitter, the said coordinate-voltages being appliedto a pair of harmonic filters each filter having its storage elements divided into two groups connectable simultaneously to thecoordinate deflectors of the oscilloscope. Thefilters are alternately energized under control of-the received coordinate signals" and the cathode-ray tube luminescent spot is-intermitt ently blanked off in timed coordination with-the utilization of the energy in the storage elements of the filters "in order that thecoordinate signals are applied 1,

correctly to the coordinate deflectors of the oscilloscope. v H

A still further feature relates to the novel organization, arrangement and relative interconnection of parts which cooperate to provide an improved telautograph system of the cathoderaytube oscilloscopetype.

Other features and advantages not particularly enumerated will be apparent after a consideration of the following detailed descriptions and the appended claims.

Two separate rectifiedsignals representing the X and Y components of the original scanned subjectl'matte'r are received'alternately and recurrentlyat the terminals Ill. These signalsmay be produced by any well-known form of telautograph transmitter indicated diagrammatically by block l.' These signals which are referred toas X and Y signals are transmitted to the receiving terminals l '!l- '-l 0 after demodulation: and rectification, and are arranged to be simultaneously applied to the'coordinate deflection controlplatesor'eleme'nts II and "respectively of cathode-ray tube oscilloscope 13. The simultaneous application of the alternately received signals to the deflector plates of the cathode-ray tube'is' effected through the intermediary of-two rotatable'harmonic filters l4 and I5; whose rotatable elements aresynchronized and-may; be mounted on the same shaft which is driven by any suitablemotive means, for example'at the rate of-1800 For a detailed'description of these harmonic filters, reference may -be--had to abandoned application'Serial No.'59l-,894,-filed May 4, 1945, the disclosure of which isincorporated herein by reference. As disclosed in -said application, each filter comprises a bank of separate storage elements- 2, which may be either quency of recurrence of the X and Y signals combination and harmonics thereof, the rate of rotation of theicharging brush 3, should correspond to the said frequencyof recurrence. The

energy of each incremental segment of the rectified Wave form is impressed on a particular storgethersoas to alternate their respective movable the cyclical rate of rotation of the brush 3. How-- ever, undesired interference noises which do not occur at the repetition rate of the received wave will not build up during the storage cycles. Since only the desired signals on the recurring received Waves will cumulatively charge the storage elements, these filters are of a harmonic or synchronous type and, the outputs therefrom of interfering signals will be negligible in comparison with the outputs of the harmonically or synchronously selected waves. The energy stored in condensers 2 is applied by a pair of brushes 4, 5 to amplifier tubes 31, 38 without appreciable loss of energy from condensers 2 These brushes may be mechanically coupled so as to rotate'as a unit around, and at the same time making contact character, there is provided a switch which has its rotatable or movable contact arm directly grounded and is adapted to ground its associated contact 30A for a predetermined short time interval having a minimum duration corresponding to one complete revolution of the harmonic with, the respective commutator segments 6 to V which the several storage condensers are indi--- vidually connected. Alternatively, the brushes 3,

A and 5, maybe stationary and the commutator 'segmentsandicon'densers "may be mounted on a- ..suitable rotatable drum. Preferably, the brushes 4' and E'a're'dispIaced apart 180 while the brush 3 may be located substantially mid-way between brushes 4-5 around the circumference of the commutator. The filter l5'is similar to filter I4 and has brushes 1, 8 and 9, which correspond to p the similar brushes 3, 4 and s of filter 14.

The simultaneous application of signals to the vertical and horizontal defiectionplates ll and 12 of the cathode-ray tube l3, results in a visual display of. the signals on the luminescent screen of the tube. In order to compensate for the relatively short persistence of the phosphorescent screen of tube [3, each harmonicfilter alter-' nately serves the function of building-up the wave forms for a period of one character time interval, and then supplying these wave forms qrecurrently to' the cathode-ray tube for one character time interval. In other words, while the X. and Y telautograph. signals are re- ..peatedalternately in the transmission to termii-nals. lfl they are picked-up simultaneously from the harmonic filters by the brushes 4--5, or by the; brushes 8-9, and are applied simultaneously to the cathode-ray tube. The storage elementsof each of the harmonic filters which are associated respectively with each of the received X' and Y signals are arranged substantially around one-half the circumference of the harmonicfilters.

Hence the storage elements along the -sectors I! and 1-8 of filters l4 and I5 respectively' supply the signals which are applied to the horizontal deflection plate 12; and the storage elements along the segments l9 and 2B of filters l4 and I5 respectively supply the signals "which are applied to the vertical deflection plate H.

' ttand l'5 alternately deliver energy to their assoc'iated circuits for the time of character intervals and store energy received from the rectified audio signals during the interleaving character time intervals.

The timed charging and discharging functions of the X and Y sections of the two filters are controlled by three switches 21', 28 and These switches are suitably ganged tocontact arms from one to the other of the assocumulative filter. I 3

During the display of a character on tube [3, the control grid 33 is intermittently supplied with cut-ofi negative bias, and for this purpose there is provided an additional switch 3! which is suitably ganged to the brushes of the harmonic filters so as to apply this cut-off bias during onehalf revolutions of either filter, thus making sure that the X and Y signal potentials are never applied to the incorrect set of deflectorplates of tube l3. g

The resistor 34 through which the rectified audio signals are conveyed to switch 21 and thence to filters It and i5 is soselec'te'dlthat condensers 2 cannot charge appreciablyuntil many revolutions of the harmonic filter, corresponding to. a character. timeinterval. This charging causes the harmonic filters to have a waveform selectivity, as maybe understood by referencetoapplication Serial No.

591,894. B this means the efiect of interference can be greatly reduced. The separate rectified audio signals received at terminals [0, flow through switch 21 and through input brushes 3 or 1 to the harmonic filters id or IS. The signals leave the harmonic filters via output brushes 4,. 5, 8 and 9, and passthrough v switches Hand 29 to the grids 35 and 36 of amplifier tubes 31 and 38. The signal to be applied. to the horizontal deflectionpl'ates l2v is fed to the control grid. 35 of amplifier tube 31;and the signalto be applied to the vertical deflection plates His fed to the-control grid 36 oftube 38. The tubes 3'! and 38 are identical as are the respective circuits associated with them. In these two amplifier circuits the following components .are 'of equal value; resistors 39 and: 48, by-pass condensers 4i and 4-2-,;plate load resistors 43 and. M, and blocking condensers and 46 y The signals to be applied t the horizontal deflection plates [2 are passed through the lowpass LCRfi-lter associated with amplifier tube 31 which. consists of. lowfrequency inductor Al,

condensers -48and49, and. resistor Ell. This filter network eliminates the unwanted ripple arising from. the commutation of segments 6 and allows flection plates H are passed through the low- ;pass LCR. filter associatedwithamplifier tube 38 whichconsists oflowfrequency inductor 52, condensers 53 and 54, and resistor 55 Like thefilter associated with amplifier tube '37, this filter network eliminates the unwanted segment ripple which may be present in: its input and allows the remaining wantedsig-nal to be applied to the verticaldefiection plates -11 of cathode-ray tube [3 through conductor 56.

The low-pass filter networks associatedwith tubes 31 and 38 may be of any other well-known design.

The resistor 51 connected between ground and a high positive voltage supply acts as a voltage divider. The proper setting of the adjustable contacts 58 and 59 along resistor 51 provides the appropriate centering voltages for the horizontal and vertical deflection plates of the cathode-ray tube 13 as is well-known in the art.

The operation of the apparatus with relation to the various switches and the harmonic filters may be easily understood by attention to the following explanation. With the switches in the position shown, the X and Y signals received at terminals Ill are successively stored in the storage element banks I! and 19 of the filter M. The brushes 4 and 5 which transfer the signals to be applied to the horizontal and vertical deflection plates respectively are connected to the open terminals 28a and 29a of switches 28 and 29, and therefore no energy is fed to the remaining circuits. When the reception of another character is about to occur, the synchronizing means controlling the movement of switches 2'1, 28 and 29, simultaneously changes them from their full-line position to the dotted-line position completing circuits through terminals 21a, 28a and 29a. The instant this change is completed, the signal to be applied tothe horizontal deflec- 3 tion plates I2 is fed from brush 4 through switch 28 to the grid 35 of amplifier tube 31. At the same instant the signal to be applied to the vertical deflection plates H is fed from brush 5 through switch 29 to grid 36 of amplifier tube 38. These signals then pass simultaneously through the remaining circuit as previously described and cause the luminescent spot of the cathode-ray tube to follow a trace corresponding to the relative magnitudes of the original X and Y signals.

While the signals from harmonic filter l4 are being passed to the tube 13, the signals received at terminals ID are fed into the harmonic filter l5 through input brush 1. Output brushes 8 and 9 are open-circuited and the energy is stored in the storage elements of the harmonic filter l5. When this second character is completed the switches 21, 28 and 29 are automatically returned to the full-line position and the signals to be applied to the horizontal deflection plates l2 of the tube l3 are fed to grid 35 of amplifier tube 31 through brush 8 and switch '28. The signals for the vertical deflection plates ll of the tube [3 are simultaneously fed to the grid 38 of amplifier tube 38 through brush 9 and switch 29. These signals are then displayed on the cathode-ray tube l3 in a manner similar to that mentioned for the first character.

In the embodiment as described, the switches 21, 28 and 29 alternate once each character and the switch 38 is closed for one complete filter shaft revolution at the beginning of each separate operation representing a new character and thereby all of the storage elements associated with the filters are preliminarily discharged directly to ground at switch 38. The cut-oft voltage applied to switch 3| is applied intermittently to the control grid 33 of tube l3 during the entire character displayoperation so as to render tube l3 inoperative while brush 4 (or 8) is picking up the Y signal and brush 5 (or 9) is picking up the X signal, and to render tube [8 operative while brush 4 (or 8) is picking up the X signal and brush 5 (or 9) is picking up the Y signal.

' whatisclaimedist 1 .l .1

1. In a visual signal reproducing system-of th kind adapted to alternately receive two sets of signals over a single-channel representin respectively the spacial coordinates of-a moving point to be reproduced;-a cathode-ray tube-oscilloscope having coordinate beam-deflecting elements, a bankoi electric energy storage elements, means to alternately charge'each of said elements under control respectively of said separate" sets of signals so that the stored energy in each element represents a corresponding incremental-segment of the wave form of said signals, a, pair of channels leading from said bankrespectively to each of said coordinate deflecting elements, and means simultaneously to discharge said stored energy in pairs of storage elements over said respective channels'.-' 8 1 '1 2. A visual signal "reproducing systemacco'r'ding to claim 1 inwhich said sets ofsig'nalshave a regular recurrent-frequency component and the product of the number of storage elements in said bank and the cyclical rate of charging there'- of bears an integral relation to the said regular frequency componentof said signals.

3. A visual signal reproducing system according to claim 1 in which said bank is in the form of a harmonic filter having means to charge said storageelements ata predetermined cyclical rate synchronized on said signal Wave, means-t0 discharge said storage elements, and means to introduce a predetermined time lag between the charge and discharge of each of said elements corresponding to any of said incrementalse'gments. I l

4. A visual-signal reproducing system according to claim 1 in which saidstorage elements" are in the form of condensers, said condensers being provided with a charging brush and a pair of discharge brushes, all the brushes being rotated in unison, one discharging brush being connected to control the horizontal deflection of the oscilloscope, and the other discharging brush being connected to control the vertical deflection of the oscilloscope.

5. In a visual signal reproducing system of the kind adapted to receive two sets of signals representing respectively the spacial coordinates of a moving point to be reproduced, a cathode-ray tube oscilloscope having coordinate beam-deflectin elements, a pair of harmonic filter and energy storage devices, each device comprising a bank of condensers, means to receive said sets of signals in alternate periodic time sequence, means to apply said signals alternately for equal time periods to said devices, first and second discharge brushes for each device, means connecting the first discharge brush of one device to one of the deflecting systems of the oscilloscope and for simultaneously connecting the second discharge brush of the other device to the other deflecting system of the oscilloscope, and switch means operated in timed relation with respect to the rate of cyclical charging of said condensers for connecting the said second brush of the first device to said one deflecting system of the oscilloscope and simultaneously connecting the said first discharge brush of the other device to said other deflection system of the oscilloscope.

6. A system according to claim 5 in which said switch means comprises a pair of switches, each switch having a first and a second contact, the first and second contacts of one switch being connected respectively to the said first discharge brushes of both said devices, and the first and reesnea second contacts 6f the otherrsmtehz i mersco nested: respectively 1701? the; secondzi discharge brushessofibotrrsaid d'evices and eachswitch nay-. inggzazdnevabieecontactiforealternateiy connecting itssassociated-ifirst andrvsecond@contacts invcincuit witmtiie :corresponding defiection isystems of-hthe oscilloscope L? .A system: accordingto claim; 5;: in which axthirdiswitch'.;is.:providedt.for.;rcontrollin ftheeah ternate applicatiemofrthe receivedgisetslgf signals tozsaidr devices, I I

851x112,'telautog 'anmsystem a cathodewayiube oscfldoscdpemeproducer, means to ,alternatelx ree cetve ztwoavoltagese oven a -.sing1e .-channe1t repre-f sentingg, the? X? and; Y? coordinates 013. each ppint 20f 2 the.te1auto graph imagerto the :reproduced, azmaimofisynchronous filters, means tuaiternate: 1y apply, the received signals to said filtersiinralg ternate periodic sequen ce sotthatieach'filter,builds up:=thes.,-reeeived iwaveeforms-Efor; a: predetermined timwintervah ,each .of said .filters having a ,pair of specially disgl-aceddischarge brushes corre spending;respectivem.tortheflXii and. Y. coor= climates:rot{theereceivedrtelautograph signals, and means for; applying aid wave f6rmsirom "each of saidfiltersetoacorresppnding defiection system of said oscilloscope; said last-named means connect ing onlwthewx discharge brush :01? one filterv to pnenof-r the, oscilloscope. deflectiomsystems; while onlyg; the; Y comppnent rdischarge; brushsof, the

other/r filtemis; connected to.. the other deflection systemiofatheoscilloscope r 9; Inia ;te1aut0g;raph system; means t0 receive inzalternatestime periddic sequence,;X.f and 'fYi" spacial components of a t'elautograph message,

a zcathode=ray tubeloscilloscopeehaving copridinate beai'm-deflecting systems, at. pair of; harmonic fiiters; ancyclicallwoperatinggswitcir forr-apnlyin the receivedzffx i"andzfYisignalsr tossaidafiifiers alternately;.atpeir oi;discnarseebrusheesfqreeaqh filterrf0rrcontr mngg espe tiyems heitube,defies:

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harmonicrfilter 'andmaid. switching means each filterwhaving amank of;,electrical.' storaggmneans}v dis hargebrushes endelectriqal switclzling me nsv associated witnthetou pl t ofisaid harmonicfiltera;

I a ush-124111,. amplifier; controlled by; said;fi1ters-,.

1ow;p ass.-.fi1ter meansseiectrically, connected t6 pnsh rpu llflamplifiersionsuppressing ,the Tip; 21?: 156 arising at saidiHters; and. means rsimiil taneously connecting said 1 w=pass filter nieanfito the-respective, r vertical i and-L horizontal; deflection e1en ents ,of; said cathodeeray, tubes.

. GILBERT R. CLARK;

REFERENCE$T CITED 

